Connect with us

Audio pitch adjustment circuit

Discussion in 'Electronic Basics' started by Chris W, Mar 24, 2006.

Scroll to continue with content
  1. Chris W

    Chris W Guest

    I want to take an 8 ohm, mono, audio signal that could be as high as 3
    watts, and input it into a circuit that would allow adjustment of the
    pitch up or down. Then it needs to output to a speaker with out
    affecting the power very much. Would a circuit that could do this be
    very hard to design? Or are there some out there already I can just
    copy and build?

    On a related note can some one tell me where I can find a simple audio
    filter to filter out any frequency over 900hz and pass anything
    lower.... I know I can probably find it on google but thought I would
    ask while I am writing about the other circuit.

    Chris W

    Gift Giving Made Easy
    Get the gifts you want &
    give the gifts they want
    One stop wish list for any gift,
    from anywhere, for any occasion!
  2. Deefoo

    Deefoo Guest

    Get yourself a pitch shifter (see the link for an example) and feed it into
    an amp. Get yourself an equalizer for the 900Hz stuff.

  3. Bob Masta

    Bob Masta Guest

    Pitch shifting is decidedly non-trivial, and doing it well is much
    harder. This is one of those times when you need to carefully
    examine what you are trying to accomplish and see if there is
    some other way. We'd be glad to help with that if you explain
    what the ultimate goal is.

    If the input signal is known to be a pure sine, then you can
    use an SSB approach. This is still a bit involved if the sine can
    have a wide frequency range, since it typically requires a 90 degree
    phase splitter. If there are harmonics in the input, this won't
    give a harmonic output, however.

    Audio pitch shifters are almost always done digitally. Some
    very sophisticated algorithms are involved, and even still they
    often have artifacts.
    You need to provide more details here as well. Filters have
    sloping roll-offs, so you have to decide just how steeply you
    need to cut off above 900 Hz. If you can tolerate only 6 dB/octave,
    then you can do this with a resistor and capacitor. Beyond that,
    there are plenty of tradeoffs along with increasing complexity.

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Home of DaqGen, the FREEWARE signal generator
  4. Chris W

    Chris W Guest

    I have a Kenwood TS 440SA Ham radio HF transceiver. In Morse code mode
    the BFO is set for a frequency of 800 hz. I would prefer a lower
    frequency. If the signal is strong and you don't need any filtering
    then you can simply turn on the RIT function and adjust the frequency
    quite a bit either way. However if the 250hz narrow band CW filter is
    being used, you are very limited in how much you can adjust the
    frequency up or down. So that is what I want to do. I don't remember
    the exact output of the radio to the external speaker, but I am pretty
    sure it is 2 or 3 watts.

    Same radio, but this time on transmit. What it actually transmits is
    fine, but the in Morse code mode, instead of the 800hz tone it is
    supposed to sound when you are keying, it sounds 800hz and at least 2
    harmonics of 800 hz. I just don't like the way that sounds, so I want
    to filter out the harmonics enough that I won't notice it. I'm not sure
    if 6db per octave is enough. Last night right before MusicMatch crashed
    my computer again, I had found a low pass filter circuit that claimed 24
    or 36db/octave, can't remember. It was comprised of 2 op amps and
    several capacitors and resistors. It didn't give a specific op amp and
    I know nothing about them, so when I go to to order one, I
    will need something more specific to narrow it down from what I am sure
    will be thousands of choices. It was set at 1000hz which would probably
    work fine given it's high drop off rate. Now that I think about it, the
    transceiver probably sends the harmonics to the transmitter too, but the
    bandwidth of the TX in CW mode is probably narrow enough to reject the

    Chris W

    Gift Giving Made Easy
    Get the gifts you want &
    give the gifts they want
    One stop wish list for any gift,
    from anywhere, for any occasion!
  5. Er..., well yes, they have to. An *true* up-shifter is a time machine.
    You cant make things happen faster (before) they occurred.

    Kevin Aylward
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.

    "There are none more ignorant and useless,than they that seek answers
    on their knees, with their eyes closed"
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day